This invention relates generally to optical systems which sense the presence of a target. Specifically, the present invention relates to optical systems which utilize a conical beam or field of view. More specifically, the present invention relates to a target detector which is useful to a missile that must detect the presence of a target.
Such missiles operate in an environment which causes the missiles to experience severe shocks and vibrations. Accordingly, optical target detection systems used in such missile must also withstand the severe shock and vibration environment. Additionally, such missiles are typically not reusable and are produced in large quantities. Thus, optical target detection systems used in these missiles should be inexpensive.
Optical systems previously used with these missiles suffer many drawbacks. For example, some optical systems require a lens which completely surrounds the missile. Such a design is not structurally sound in a severe shock and vibration environment because the strength of the missile depends upon the relatively low strength of the lens. Furthermore, some optical systems tend to produce a focal point at the center of the missile. These systems tend to require too much volume within the interior of the missile. Additionally, such systems tend to represent non-imaging systems which smear the optical image so that no point-to-point correspondence exists between the target being sensed and the target's image. As a consequence, such optical systems do not provide azimuth information. Still further, some optical systems require a relatively large detector which is expensive and which generates a noisy output signal when compared to smaller detectors.
Other prior art optical systems utilize complicated multiple lens or multiple mirror arrangements. Such complicated arrangements represent unreliable systems in the severe shock and vibration environment and additionally tend to operate only over a small half conic angle range. As a consequence, such systems tend to be relatively expensive and to allow only a single conical beam.
Other prior art optical detection systems utilize lenses or mirrors in which the lens or mirror axis is not parallel with the missile axis. An unsymmetrical output response with azimuth results. In other words, such systems do not provide a true conical response because the output signals may change several DB depending upon the angle of view.
As another example, some prior systems do not allow electronic steering of the optical beam. Thus, either the optical target detection system provides a limited amount of information or a mechanical steering structure must be employed. Mechanical steering structures are relatively expensive and unreliable in the severe shock and vibration environment that a missile experiences.